fix: harden remaining display-layer surfaces against non-string tool args

Consolidation follow-up on top of @liuwei666888's compressor fix (#52431)
and @Frowtek's ACP render guard (#62588) — completes the class fix across
every display-layer consumer of tool-call arguments:

- agent/context_compressor.py: wrap _summarize_tool_result in a
  never-raises backstop (same pattern as get_cute_tool_message and the
  ACP guard). The per-branch _str_arg coercions keep summaries
  informative; the wrapper guarantees compression can never crash-loop
  on a summary branch we didn't anticipate. Also reject non-dict parsed
  args (a JSON list/scalar would crash every args.get call).
- agent/display.py: build_tool_preview's process branch sliced
  session_id/data without coercion — crashed build_tool_preview and
  build_tool_label on the live tool-progress callback (probed live:
  TypeError 'int' object is not subscriptable). Coerce like the
  sibling branches.
- tests: backstop fuzz matrix (16 tools x 6 hostile value shapes),
  fallback-shape contracts, display process-preview regressions,
  non-dict args guard.

agent/context_compressor.py

@@ -613,11 +613,30 @@ def _summarize_tool_result(tool_name: str, tool_args: str, tool_content: str) ->
         [terminal] ran `npm test` -> exit 0, 47 lines output
         [read_file] read config.py from line 1 (1,200 chars)
         [search_files] content search for 'compress' in agent/ -> 12 matches
+
+    Never raises: models sometimes emit non-string argument values (bool,
+    int, None) and the args here come from persisted session history, so a
+    single malformed historical call must not crash compression — which
+    retries on the same history and would crash-loop. Individual branches
+    coerce the values they slice/measure (keeping summaries informative);
+    this wrapper is the backstop for anything they miss.
     """
+    try:
+        return _summarize_tool_result_unguarded(tool_name, tool_args, tool_content)
+    except Exception as exc:  # noqa: BLE001 — a summary must never crash compression
+        logger.debug("Tool-result summary failed for %s: %s", tool_name, exc)
+        _len = len(tool_content) if isinstance(tool_content, str) else 0
+        return f"[{tool_name}] ({_len:,} chars result)"
+
+
+def _summarize_tool_result_unguarded(tool_name: str, tool_args: str, tool_content: str) -> str:
+    """Build the summary line (unguarded; see ``_summarize_tool_result``)."""
     try:
         args = json.loads(tool_args) if tool_args else {}
     except (json.JSONDecodeError, TypeError):
         args = {}
+    if not isinstance(args, dict):
+        args = {}
 
     content = tool_content or ""
     content_len = len(content)

agent/display.py

@@ -462,13 +462,14 @@ def build_tool_preview(tool_name: str, args: dict, max_len: int | None = None) -
         sid = args.get("session_id", "")
         data = args.get("data", "")
         timeout_val = args.get("timeout")
-        parts = [action]
+        parts = [str(action) if action else ""]
         if sid:
-            parts.append(sid[:16])
+            parts.append(str(sid)[:16])
         if data:
-            parts.append(f'"{_oneline(data[:20])}"')
+            parts.append(f'"{_oneline(str(data)[:20])}"')
         if timeout_val and action == "wait":
             parts.append(f"{timeout_val}s")
+        parts = [p for p in parts if p]
         return " ".join(parts) if parts else None
 
     if tool_name == "todo":

tests/agent/test_summarize_tool_result_type_safety.py

@@ -187,6 +187,13 @@ class TestEdgeCases:
         result = _summarize_tool_result("terminal", None, "output")
         assert "terminal" in result
 
+    def test_non_dict_json_args(self):
+        """Args that parse to a non-dict (list/scalar) should not crash."""
+        result = _summarize_tool_result("terminal", json.dumps([1, 2]), "output")
+        assert "terminal" in result
+        result = _summarize_tool_result("terminal", json.dumps("bare"), "output")
+        assert "terminal" in result
+
     def test_unknown_tool_name(self):
         """Unknown tool name should return generic summary."""
         args = json.dumps({"foo": "bar"})
@@ -205,3 +212,75 @@ class TestEdgeCases:
         result = _summarize_tool_result("terminal", args, '{"exit_code": 0}')
         assert "terminal" in result
         assert "ls" in result
+
+
+class TestBackstopWrapper:
+    """The outer guard: NO input shape may raise out of _summarize_tool_result.
+
+    Compression retries on the same persisted history, so an escaping
+    exception here becomes a crash loop. The wrapper returns a minimal
+    '[tool] (N chars result)' summary when a branch fails.
+    """
+
+    def test_never_raises_matrix(self):
+        """Fuzz the per-tool branches with hostile value shapes."""
+        hostile_values = [None, True, 42, 3.14, ["a"], {"k": "v"}]
+        tools = [
+            "terminal", "read_file", "write_file", "search_files", "patch",
+            "browser_navigate", "web_search", "web_extract", "delegate_task",
+            "execute_code", "skill_view", "vision_analyze", "memory",
+            "cronjob", "process", "totally_unknown_tool",
+        ]
+        keys = ["command", "path", "content", "pattern", "url", "query",
+                "urls", "goal", "code", "name", "question", "action",
+                "target", "session_id", "mode", "offset", "ref"]
+        for tool in tools:
+            for value in hostile_values:
+                args = json.dumps({k: value for k in keys})
+                result = _summarize_tool_result(tool, args, "x" * 250)
+                assert isinstance(result, str) and result, (tool, value)
+
+    def test_backstop_fallback_shape(self):
+        """When a branch does fail, the fallback names the tool and size."""
+        from unittest.mock import patch as _patch
+        with _patch(
+            "agent.context_compressor._summarize_tool_result_unguarded",
+            side_effect=TypeError("boom"),
+        ):
+            result = _summarize_tool_result("terminal", "{}", "y" * 300)
+        assert result == "[terminal] (300 chars result)"
+
+    def test_backstop_handles_non_string_content(self):
+        from unittest.mock import patch as _patch
+        with _patch(
+            "agent.context_compressor._summarize_tool_result_unguarded",
+            side_effect=TypeError("boom"),
+        ):
+            result = _summarize_tool_result("terminal", "{}", None)
+        assert result == "[terminal] (0 chars result)"
+
+
+class TestDisplayPreviewTypeSafety:
+    """Sibling site: agent/display.py previews run on the live
+    tool-progress callback and crashed on non-string process args."""
+
+    def test_process_preview_non_string_session_id(self):
+        from agent.display import build_tool_preview
+        assert build_tool_preview("process", {"action": "poll", "session_id": 123}) == "poll 123"
+
+    def test_process_preview_non_string_data(self):
+        from agent.display import build_tool_preview
+        result = build_tool_preview(
+            "process", {"action": "submit", "session_id": "abc", "data": 42}
+        )
+        assert result == 'submit abc "42"'
+
+    def test_process_preview_none_action(self):
+        from agent.display import build_tool_preview
+        result = build_tool_preview("process", {"action": None, "session_id": "abc"})
+        assert isinstance(result, str)
+
+    def test_process_label_non_string_session_id(self):
+        from agent.display import build_tool_label
+        result = build_tool_label("process", {"action": "poll", "session_id": 123})
+        assert isinstance(result, str)